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Target lost after meridian flip

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The other day I was shooting a target (Deer Lick Group).

After a meridian flip, capturing resumed but it was off by several degrees in declination,
In the attached log you can see before the meridian flip, the telescope was pointing at RA= "22h 38m 08s" DEC= " 34° 31' 49\"".
After the flip there is a plate solving which results in Solution coordinates: RA (22h 37m 39s) DEC ( 37° 24' 54\") Telescope Coordinates: RA (22h 35m 02s) DEC ( 35° 50' 31\")".
Finally we find a "Syncing to RA (22h 37m 39s) DEC ( 37° 24' 54\")".

I do not understand why Ekos does not try to slew back to the original coordinates but just syncs and continues capturing from the wrong coordinates.

Logs in attachment (Kstars 3.5.9)

Thanks in advance,

Paul
1 year 7 months ago #84786
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Quick guess: Was the action in the align tab set to 'sync' instead of 'slew to target'?
1 year 7 months ago #84792

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Indeed, it is set to sync.
However, I only use this tab to do initial plate solving. I had no idea this tab was also relevant for meridian flip. Did I miss any documentation ?
Last edit: 1 year 7 months ago by Paul.
1 year 7 months ago #84799

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Probably not. I assume it is like with other tabs (focus, guiding) where you can set options that will be used for the automatically triggered actions. If you set wrong parameters there, those would also fail when triggered during a sequence.
Not sure if it is possible to override settings. For an alignment after a MF, enforcing 'slew to target' mode surely would be reasonable. Something for the gurus to discuss I assume ;)
1 year 7 months ago #84800

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It should (and at least used to) be "slew to target". I'll check it...
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1 year 7 months ago #84806

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Thanks.

IMHO the software should _always_ slew to the target after a MF.
1 year 7 months ago #84807

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Paul, could you please post the entire log? I would like to see what you did before the meridian flip happened.

And I have to withdraw my statement above. Using alignment with sync only is problematic in combination with the meridian flip. The explanation is as follows: Assume you slew the mount to a certain position. This slew is stored by the Alignment module as target position. A subsequent "sync" does not change this, the Alignment module still assumes that the position you slewed to was the one you intended to use subsequently.

Therefore, after a meridian flip, the Alignment module will slew to the target position and not the position you synched afterwards. We may discuss whether the Alignment module should forced to switch to "slew to target". But this will not solve your problem, it will use a different target than you used for capturing (assuming that you started capturing after a sync).

My recommendation is using the scheduler for capturing with EKOS. It gives the expected automation if you want to run your scope capturing unattended. You may use the Capture module standalone, but it needs experience to do things right (see above) and is not as robust as the Scheduler.

Wolfgang
1 year 7 months ago #84832

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Not sure if I understand your explanation. If I only use the Capture module and set 'slew to target' in Alignment tab, will it be okay or not according to you ?

Yes, I am attaching the full log here.
1 year 7 months ago #84841
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Using „slew to target“ should solve the problem.
1 year 7 months ago #84842

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It is how I always use it (I also only use the capture module), and MF plus re-targeting works perfect here.
1 year 7 months ago #84853

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Paul, the log shows that you did what I assumed above. You slewed to RA: 22:38:06 - DEC: 34:31:49, but the sync showed that the mount was in fact at RA: 22:38:08 - DE: 34:31:37. When the meridian flip started, it slewed again to RA: 22:38:06 - DEC: 34:31:49 and not to the point where your capture sequence was running.

As I said before, I would recommend using "slew to target" during alignment so that you are sure that after a MF, the mount will be placed at exactly the same position. Using sync is only for building the alignment model but not for capturing.

HTH
Wolfgang
1 year 7 months ago #84862

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